Research On Basic Problems And Foaming Materials Of Silicone Rubber Materials

Silicone rubber has excellent high and low temperature resistance and the food hygiene performance,widely used in household appliances,electronics,medical and automotive industry with the expansion of silicone rubber application and improvement of technology,the research of some basic problems of the silicone rubber material is more and more attention,such as home appliances industry demand for silicon rubber smell,medical products to silicone rubber low temperature performance requirements.Based on silicone rubber material,the odor,shrinkage and crystallization behavior of vulcanized silicone rubber at low temperature were studied.Firstly,the peculiar smell of silicone rubber is studied.Peroxide vulcanized silicone rubber is one of the difficult problems in silicone rubber industry because of its unpleasant smell.In this paper,by studying the causes of odor,the methods to eliminate the odor of silicone rubber,and the influence of these methods on the physical and mechanical properties of silicone rubber were explored.The results showed that alcohol small molecule residues were generated in the process of double 25 vulcanized silicone rubber.The post cure can effectively reduce the small molecule residues and reduce the smell grade of silicone rubber.When The post cure time reached 3h,the smell grade basically did not change.With the increase of The post cure time,the apparent crosslinking density of silicone rubber gradually increases,the hardness gradually increases and tends to be stable,the elongation at break becomes lower and lower,and the tensile strength increases first and then decreases.In order to further remove the residual small molecules,self-made modified calcium hydroxide was added to the silicone rubber material,and the smell grade of the silicone rubber material decreased from 3.5 to 2 With the increase of the dosage of modified calcium hydroxide,the apparent crosslinking density and tensile strength of the silicone rubber material increased first and then decreased,and the breaking elongation decreased first and then increased.The shrinkage of silicone rubber will affect the dimensional accuracy of silicone rubber products.The paper studied the influence of vinyl content of silicone rubber,the amount of silica and cure temperature on the shrinkage of silicone rubber materials.The results show that with the increase of the vinyl content of silicone rubber,the apparent crosslinking density of silicone rubber material increases,the tensile modulus increases,the stress relaxation degree decreases,the movement degree of silicone rubber molecular chain decreases and the sample size shrinkage decreases.With the increase of silica content,the hardness of silicone rubber material gradually increased,tensile strength increased first and then decreased,apparent crosslinking density increased,silica physical adsorption capacity of silicone rubber molecular chain increased,the gap between the molecular chain decreased,silica rubber sample vulcanized after the movement of molecular chain decreased,sample size shrinkage decreased.With the increase of cure temperature,the shear stress relaxation degree of silicone rubber material at this temperature is higher,the apparent crosslinking density decreases first and then flattens out,the kinetic ability and degree of silicone rubber molecular chain are improved,and the size shrinkage rate of sample after vulcanization is increased.Crystallization of silicone rubber will affect the low temperature resistance of silicone rubber material.The results showed that the increase of silica content provided the heterogeneous nucleation process of silicone rubber,the crystallization peak temperature increased from-69.12? to-66.97?,and the crystallization time was gradually shortened.The longer curing time increases the chemical cross-linking point of silicone rubber,the movement ability of molecular chain decreases,the stability of three-dimensional stacking of chain segments increases at high temperature,and the crystallization temperature increases from-78? to-67.96?,and the crystallization time decreases.The second stage vulcanization of silicone rubber reduces the crystallization temperature from-67.96? to-69.83?,and the curing time is extended from 300 s to 800 s.The non-isothermal crystallization kinetics of silicone rubber was studied by Jeziorny method and Mo method,and isothermal crystallization kinetics was studied by Avrami method.In the isothermal crystallization process and non-isothermal crystallization process,there is a good linear relationship between the early crystallization behavior and the kinetic equation,indicating that the kinetic equation can describe the early crystallization behavior of silicone rubber.At the late crystallization stage,due to the collision between crystal regions,the crystallization mode changes and the crystallization behavior is no longer carried out according to the kinetic equation.At last,the influence of formulation system and process conditions on the structure and properties of silicone rubber foam material was studied.With the increase of vinyl content and silica content,the viscosity of silicone rubber materials is improved,and the formation and growth of bubbles are restricted,and the hardness and density of silicone rubber foam materials are gradually improved.As the amount of crosslinking agent increases,the degree of Three-dimensiona network increases,and the bubbles produced are enclosed in silicone rubber,the hardness and density of silicone rubber foam material decrease.With the increase of zinc oxide dosage,the decomposition rate of foaming agent increases,the density of silicone rubber foam decreases first and then increases,the hardness decreases gradually,and the volume shrinkage decreases first and then increases.With the increase of foaming agent dosage,gas production increased,and the volume of silicone rubber foam gradually increased after molding,but the volume shrinkage rate gradually increased.The interface flexibility of foaming agent and silicone rubber can be increased by preparing paste foaming agent and silicone oil,or mother gum can be prepared by foaming agent and silicone rubber,and the growth size and distribution of bubble holes in silicone rubber foam material can be more uniform.